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Vestibulocochlear or VIII cranial nerve

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Vestibulocochlear or VIII cranial nerve The Vestibulocochlear nerve has two components, with the cochlear provides innervation to the hearing apparatus while the vestibular branch is concerned with balance. Conduction deafness results from interference with the transmission of sound waves in the external canal or middle ear to the organ of Corti. In sensorineural hearing loss, the lesion can be in the inner ear, the vestibulocochlear nerve or the brain. Because of the extensive bilateral connections of the ear, unilateral sensorineural hearing loss is usually due to lesion of the nerve nucleus or the nerve itself. Bilateral hearing loss can be either due to a central lesion or bilateral exposure to toxins and infectious agents. • Auditory Component - Look o See if the child is wearing a hearing aid and remove it, while testing for hearing impairment. o Examine the pinna and look for scars behind the ears. o Do an otoscopic examination of both ears. Look for wax or other obstruction in the external auditory meatus and perforation of the tympanic membrane. - Whisper test The Whisper Test is a screening test for hearing loss in older children and correlates with a hearing loss of 30 decibels. o Stand about two feet behind the child on one side so that they cannot read your lips. o Place your finger on the external auditory meatus of the ear which is not being tested to mask the sound. o At the end of your exhalation, whisper a word with two distinct syllables towards the ear which is being tested. o Ask the child to repeat the two syllable word. o Repeat the test on the other side - Distraction test It is a behavioural screening test of hearing for babies between six and eighteen months. The test capitalises on ... ... middle of paper ... ...ormally, the child should be able to turn the head against resistance. Hypoglossal or XII cranial nerve The Hypoglossal nerve provides motor supply to the intrinsic muscles of the tongue. • Look - Ask the child to open the mouth and inspect the tongue on the floor of the mouth. Observe the tongue for signs of wasting or fasciculations. - Next, ask the child to protrude their tongue 'Stick out your tongue'. Look for deviation of the tongue from midline. In peripheral hypoglossal lesion, there will be atrophy and fasciculations and the tongue will deviate towards the side of the lesion. In central lesion, there is spastic paralysis of the tongue without atrophy or muscle fibrillation and paralysis and the tongue deviates to the opposite side. • Motor Component - Ask the child to push the tongue into each cheek while you press from outside with your finger.

In this essay, the author

  • Explains that the vestibulocochlear nerve has two components: the cochlea provides innervation to the hearing apparatus while the vestibular branch is concerned with balance.
  • Advises parents to remove hearing aids from children while testing for hearing impairment.
  • Recommends performing an otoscopic examination of both ears. look for wax or other obstruction in the external auditory meatus and perforation of the tympanic membrane.
  • Explains that the whisper test is a screening test for hearing loss in older children.
  • Advises to stand about two feet behind the child on one side so that they cannot read your lips.
  • Advises placing their finger on the external auditory meatus of the ear which is not being tested to mask the sound.
  • Suggests that at the end of an exhalation, whisper a word with two distinct syllables towards the ear which is being tested.
  • Explains the behavioural screening test of hearing for babies between six and eighteen months. the test capitalises on the infant’s instinct to turn and locate a quiet sound presented at ear level outside the visual field
  • Recommends asking a helper (this could be your examiner) to stand in front of the child and capture their attention.
  • Explains how to stand behind the child on a horizontal level at 45o outside the baby's field of vision at one metre.
  • Advises placing the base of a vibrating 256 hz tuning fork in the centre of the child's forehead.
  • Explains that the sound should be heard equally in both ears.
  • Compares sensorineural deafness and conductive hearing loss, stating that the sound is heard better in the normal ear.
  • Recommends placing the base of a 512 hz vibrating tuning fork on the mastoid process, behind the ear.
  • Advises that when the child says "now", remove the fork from the mastoid process and place the tuning prongs about 1 cm from external auditory meatus.
  • Explains that normally the sound is audible at the external meatus.
  • Explains that in sensorineural deafness due to universal reduction of air and bone conduction, the note is audible at the external meatus similar to a normal child.
  • Explains that bone conduction is better in conductive hearing loss and no note is audible at the external meatus (rinne negative).
  • Explains that impaired vestibular function is a cause of difficulty in maintaining posture, the others being defective proprioception and vision.
  • Explains romberg's test, where the child sways or falls to the side of the labyrinthine lesion when the eyes are closed.
  • Explains unterberger's stepping test: ask the child to walk on the same spot (stationary stepping) with their eyes closed and arms outstretched for 30 seconds.
  • Explains the hallpike manoeuvre for positional nystagmus, which is not normally performed in the exam.
  • Explains that other tests of vestibular function, such as the oculocephalic, are not performed in the exam setting.
  • Explains that these two nerves are responsible for swallowing, phonation, guttural and palatal articulation and are tested together in view of their close functional relationship.
  • Asks the child to open the mouth and inspect the soft palate, uvula and pharynx.
  • Explains that in unilateral tenth nerve palsy, the edge of the soft palate rises symmetrically and the uvula remains in the midline.
  • Explains that hoarseness of voice may occur with unilateral recurrent laryngeal nerve palsy (x nerve).
  • Describes the symptoms of recurrent laryngeal nerve palsy.
  • Advises the child to swallow a sip of water and watch for any difficulty in swallowing, nasal regurgitation or coughing.
  • Explains that soft palate does not rise and occlude the nasopharynx resulting in air leak through the nose.
  • Opines that testing pharyngeal sensation and the gag reflex are unpleasant for the child and should be omitted unless there is dysarthria or dysphagi
  • Explains that in ix nerve palsy, sensation is lost in the pharynx and posterior tongue.
  • Explains that there is reflex contraction of the soft palate and the child will gag. intact sensation but absent gag suggests tenth nerve palsy.
  • Opines that quinine should be used since the posterior third of the tongue, is sensitive to bitter taste.
  • Recommends inspecting the sternocleidomastoid muscles for wasting or asymmetry, and palpating the muscles to assess their bulk.
  • Explains trapezius: stand behind and ask the child to shrug their shoulders as hard as possible. place your hands on the shoulders and press down.
  • Explains that to test the left sternocleidomastoid, the child should be able to turn the head against resistance.
  • Asks the child to open the mouth and inspect the tongue for signs of wasting or fasciculations.
  • Explains that in peripheral hypoglossal lesion, there will be atrophy and fasciculations, and the tongue will deviate towards the side of the lesions.
  • Asks the child to push the tongue into each cheek while you press from outside with your finger.
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